1. Field of the Invention
The present invention generally relates to a symbol boundary detection method, and more particularly to a channel estimation and symbol boundary detection method in a digital video broadcasting-terrestrial 2 (DVB-T2) system.
2. Description of Related Art
An orthogonal frequency division multiplexing (OFDM) system comprises a high-efficiency multi-path modulation/demodulation technology which utilizes a multi-carrier to transmit OFDM signals, so as to improve data transmission rate. Recently, OFDM technology has been used in various wireless communication systems such as the digital video broadcasting-terrestrial 2 (DVB-T2) system.
A DVB-T2 signal is constructed by super frames, which consist of several T2-frames, to be transmitted in the DVB-T2 system. With reference to FIG. 1, a structure diagram of a T2-frame is shown in which the T2-frame 1 is composed of OFDM symbols, including one first preamble symbol (P1 symbol) 11, several second preamble symbols (P2 symbol) 13 and data symbols 15. To receive DVB-T2 signals, P1 symbol 11 should first be detected and decoded for key parameters such as the transmission type, the P2 symbols 13 then can be successive decoded to obtain the content of the data symbols 15.
The DVB-T2 signals are encapsulated into several packets as the T2-frame 1 structure which are transmitted to the receiver via plural path channels. The channel impulse response (CIR) is usually under perfect channel, to avoid the problem of inter-symbol interference (ISI), a serial of a cyclic prefix (CP) information, as guard interval (GI), is additionally added between symbol packets generally. Furthermore, in order to avoid inter-symbol interference effectively, especially in the multi-path scheme, the symbol boundary should be positioned so that the least-possible ISI is incurred when receiving DVB-T2 signals.
FIG. 2 shows a conventional symbol boundary detection scheme. As illustrated in FIG. 2, the packets 23 as the T2-frame 1 structure are transmitted via plural path channels (Pa1,Pa2), and the cyclic prefix information is added prior to each of the packets 23. Under the channel, a typical symbol boundary detection scheme will position the OFDM symbol window 25 according to the first propagation path (Pa1), as shown by the dash-line frame in FIG. 2. Once the packet error is occurred when decoding the received signals by the present positioned OFDM symbol window 25, it needs to shift the position of the OFDM symbol window 25 and then detect whether the packet error is occurred. Repeat the above steps until the least-ISI-achieving OFDM symbol window 25 is detected. However, one P1 symbol 11 and several P2 symbols 13 must be decoded in order as long as the position of the OFDM symbol window 25 is adjusted. Therefore, it consumes a lot of search time.
In view of the foregoing, a need has arisen to propose a novel channel estimation and symbol boundary detection method to estimate a channel profile efficiently to further detect an optimal symbol boundary position.